There are various ways of practicing non-ellipsometric interferometric confocal far-field and near-field microscopy. Some of those known ways involve using heterodyne techniques and a detector having a single detector element or having a relatively small number of detector elements. Others involve using a step and stare method with a traditional homodyne detection method for the acquisition of conjugated quadratures of fields of reflected/scattered beams when a detector is used that comprises a large number of detector elements. x(φ) a cos φ. The respective conjugated quadrature of the field is a sin φ when the quadrature x(φ) of a field is expressed as |a|cos φ. The step and stare method and the traditional homodyne detection method are used in order to obtain for each detector element a set of at least four electrical interference signal values with a substrate that is stationary with respect to the respective interferometric microscope during the stare portion of the step and stare method. The set of at least four electrical interference signal values are required to obtain for each detector element conjugated quadratures of fields of a measurement beam comprising a reflected and/or scattered far-field or near-field from a spot in or on a substrate that is conjugate to the each detector element.
Still other ways of practicing interferometric ellipsometry involve using either a homodyne detection method or heterodyne techniques and a detector having a single detector element or having a relatively small number of detector elements.
It is also known to use a double homodyne detection method for non-ellipsometric applications based on using four detectors wherein each detector generates an electrical interference signal value used to determine a corresponding component of a conjugated quadratures of a field. See, for example, the discussion found in Section IV of the article by G. M D'ariano and M G. A. Paris entitled “Lower Bounds On Phase Sensitivity In Ideal And Feasible Measurements,” Phys. Rev. A 49, 3022–3036 (1994). In that case, the four detectors generate four electrical interference signal values simultaneously and each electrical interference signal value contains information relevant to one conjugated quadratures component.